A robot may not injure a human being or, through inaction, allow a human being to come to harm.

A robot must obey the orders given it by human beings, except where such orders would conflict with the First Law.

A robot must protect its own existence as long as such protection does not conflict with the First or Second Laws.

In later books, a zeroth law was introduced: 0. A robot may not harm humanity, or, by inaction, allow humanity to come to harm.

Certain robots developed the zeroth law as the logical extension of the First Law, as robots are often faced with ethical dilemmas in which any result will harm at least some humans, in order to avoid harming more humans.[example needed] The classic example involves a robot who sees a runaway train which will kill ten humans trapped on the tracks, whose only choice is to switch the track the train is following so it only kills one human. Even so, the robots who theorized the zeroth law only developed it as a hypothetical, almost philosophical abstraction. Some robots use this as a license to try to conquer humanity for its own protection, but others are hesitant to implement the Zeroth Law, because in practice they aren't even certain what it means. Some robots are uncertain about which course of action will prevent harm to the most humans in the long run, while others point out that "humanity" is such an abstract concept that they wouldn't even know if they were harming it or not. A few even point out that they aren't certain what qualifies as "harm": if this restriction would simply prohibit physical harm, or if social harm is also forbidden. In this last case, conquering humanity in order to implement tyrannical controls to prevent physical harm between humans (i.e. ending all human warfare) might nonetheless constitute a social harm to humanity as a whole.[examples needed][citation needed]

Adaptations and extensions exist based upon this framework. As of 2011 they remain a "fictional device".[1]

In 2013 Hutan Ashrafian at Imperial College London, proposed an additional law that considered the role of artificial intelligence-on-artificial intelligence or the relationship between robots themselves – the so-called AIonAI law.[4] This law states:

All robots endowed with comparable human reason and conscience should act towards one another in a spirit of brotherhood.

Another comprehensive terminological codification for the legal assessment of the technological developments in the robotics industry has already begun mainly in Asian countries.[5] This progress represents a contemporary reinterpretation of the law (and ethics) in the field of robotics, an interpretation that assumes a rethinking of traditional legal constellations. These include primarily legal liability issues in civil and criminal law.